Mugen 1800mAH battery - Requesting Assistance?

I received a Mugen Power 3.7v 1800mAH li-Polymer battery for the HTC Hero (Sprint) which my phone will not seem to charge. I place the battery into the phone and the second it touches the charger the LED's flash between green and orange. When I use the phones power tool it says the batteries health was "Overheat." It will also say that when not plugged in.